Silicon photodiodes are the foundation of light-detection technology; yet their rigid structure and limited area scaling at low cost hamper their use in several emerging applications. A detailed methodology for the characterization of organic photodiodes based on polymeric bulk heterojunctions reveals the influence that charge-collecting electrodes have on the electronic noise at low frequency. The performance of optimized organic photodiodes is found to rival that of low-noise silicon photodiodes in all metrics within the visible spectral range, except response time, which is still video-rate compatible. Solution-processed organic photodiodes offer several design opportunities exemplified in a biometric monitoring application that uses ring-shaped, large-area, flexible, organic photodiodes with silicon-level performance.

A solution-based method to electrically p-dope organic semiconductors enabling the fabrication of organic solar cells with simplified geometry is implemented with acetonitrile as an alternative to nitromethane.

The field of organic electronics aspires to enable the fabrication of low-cost, solution-processed optoelectronic devices with unique mechanical, electrical, optical, and chemical properties. Critical to the success of these aspirations is the ability to fabricate controlled doping profiles vertically or laterally (i.e., to a limited depth or area extension). However, the fabrication of stable doping profiles in polymer films has proven particularly challenging, as neither solution processing nor evaporation of dopants, such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), leads to vertical doping profiles due to fast diffusion on the length scale of the typical film thickness (∼100 nm). This challenge was surmounted in 2017 with the first demonstration of a successful solution-based technique to fabricate doping profiles in semiconducting polymer films through immersion into a phosphomolybdic acid (PMA) solution (Kolesov et al., 2017). Still, to date, no clear picture that explains the doping phenomena has emerged. In an attempt to identify some of the key variables that govern the PMA doping process and shed light onto why this technique produces vertical doping profiles in organic films, we here report on a study of the morphology of PMA doped semiconducting polymer films, complemented theoretically with ab initio quantum chemistry calculations. We believe these results may foster the extension of the technique to other organic optoelectronic systems.